Use of compounds containing halogen and nitrogen for reducing mercury emissions during coal combustion

Abstract

Processes and systems are provided for using bromine and / or bromide-containing compounds derived from a nitrogen-containing compound, such as ammonia, sulfamic acid, or one or more salts thereof, to reduce mercury emissions during coal combustion.

Description

Background technique [0001] In 2005, EPA published the Clean Air Mercury Standard to regulate and reduce mercury emissions from coal-fired power plants. The standard, combined with EPA's Clean Air Interstate Standard (CAIR), requires mercury emissions from coal-fired power plants to be significantly reduced since 2010. [0002] via SO 2 Controls can remove some mercury from the flue gas of coal-fired power plants. However, flue gases often contain significant amounts of elemental and oxidized mercury; while SO 2 Controls are adapted to remove oxidized mercury, not elemental mercury. Low levels of bromine, or aqueous solutions of alkali metal or alkaline earth metal salts of bromine such as calcium bromide, sodium bromide or potassium bromide, can be used to oxidize mercury in the flue gas. However, when bromide is oxidized, it results in the generation of bromine. At least some bromine can interact with elemental mercury to form non-volatile mercury salts such as HgBr 2 ...

AI Technical Summary

Problems solved by technology

An excess of bromide values ​​relative to the amount of Hg to be removed results in significant amounts of bromine remaining in the flue gas, which is known to be corrosive to scrubbing systems and other equipment in the plant